But since they'll see that criminals can easily hide their money by means of Bitcoin transactions they'll going to take actions against it.
Countering possible illegal transactions can be done with regulated system, government will requires those exchange business to provide KYC for security reason and countering those criminals and their illegal deeds.
It's possible to "counterattack" malicious actors on centralized exchanges and centralized wallet providers, because of the single point of failure (in this case, a middleman). However, we cannot say the same about decentralized counterparts. If most people begin using non-custodial mixers and decentralized exchanges, governments will have a hard time trying to enforce the rule of law. That's largely because a decentralized system is not tied to a single jurisdiction. I'd imagine how disastrous everything will be once criminals learn how to efficiently use non-custodial mixers. Governments will have no choice but to declare crypto "illegal" as their efforts become in vain.
Nonetheless, I believe there may be no need to worry about mixers becoming "illegal" in the future. There are many ways to achieve privacy outside the scope of governments and other third parties. This is possible because of the decentralized and open-source nature of crypto/Blockchain. If it were centralized, it would've been easier for governments to enforce the rule of law. I bet non-custodial mixers and privacy-oriented cryptocurrencies will rise like skyrocket once centralized mixing services come to an end. Of course, most people don't care about their privacy since they've got nothing to hide. But for businesses, privacy is crucial to protect sensitive information from prying eyes. Time will tell us the fate of privacy in Bitcoin as it becomes more popular in the mainstream world. Just my thoughts